Improve suggested notes: limit 8, threshold 0.45, show relevance scores

- Raise similarity threshold 0.30 → 0.45: only genuinely relevant notes
  shown; loosely-related notes no longer pad the sidebar
- Increase max suggested notes 3 → 8 (zero added compute — threshold is
  the real gate; the embedding call is fixed regardless of limit)
- semantic_search_notes now returns list[tuple[float, Note]] instead of
  list[Note] so scores propagate through context_meta to the frontend
- Keyword fallback notes carry score=null (no cosine similarity available)
- ChatView sidebar shows % badge on each suggested note:
  green ≥75%, amber 60–74%, muted <60%
  Hovering reveals the raw score in a tooltip

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/types/chat.ts

@@ -54,7 +54,7 @@ export interface ConversationDetail extends Conversation {
 export interface ContextMeta {
   context_note_id: number | null;
   context_note_title: string | null;
-  auto_notes: { id: number; title: string }[];
+  auto_notes: { id: number; title: string; score?: number | null }[];
 }
 
 export interface OllamaStatus {

frontend/src/views/ChatView.vue

@@ -38,7 +38,7 @@ const includedNoteIds = ref<Set<number>>(new Set());
 const includedNotes = ref<{ id: number; title: string }[]>([]);
 
 // Suggested notes — auto-found by search, not yet included
-const suggestedNotes = ref<{ id: number; title: string }[]>([]);
+const suggestedNotes = ref<{ id: number; title: string; score?: number | null }[]>([]);
 
 let prevConvId: number | null = null;
 
@@ -482,6 +482,16 @@ onUnmounted(() => {
                 <router-link :to="`/notes/${note.id}`" class="context-note-name">
                   {{ note.title }}
                 </router-link>
+                <span
+                  v-if="note.score != null"
+                  class="context-note-score"
+                  :class="{
+                    'score-high':   note.score >= 0.75,
+                    'score-medium': note.score >= 0.60 && note.score < 0.75,
+                    'score-low':    note.score < 0.60,
+                  }"
+                  :title="`Relevance score: ${note.score}`"
+                >{{ Math.round(note.score * 100) }}%</span>
                 <button class="context-note-add" @click="includeNote(note)" title="Add to context">+</button>
               </div>
             </template>
@@ -807,6 +817,18 @@ onUnmounted(() => {
 .context-note-suggested {
   opacity: 0.85;
 }
+.context-note-score {
+  font-size: 0.67rem;
+  font-weight: 600;
+  padding: 0.05rem 0.22rem;
+  border-radius: 3px;
+  flex-shrink: 0;
+  font-variant-numeric: tabular-nums;
+  letter-spacing: 0;
+}
+.score-high   { color: var(--color-success); background: color-mix(in srgb, var(--color-success) 12%, transparent); }
+.score-medium { color: #c98a00; background: rgba(201, 138, 0, 0.12); }
+.score-low    { color: var(--color-text-muted); background: var(--color-bg-secondary); }
 .context-note-remove {
   background: none;
   border: none;